Electrical Machine Cooling via Variable Flow Rate Control
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Solution Overview
Problem
Conventional cooling methods for electrical machines in hybrid vehicles result in unnecessary drag losses due to continuous contact with coolant, and inefficient energy usage as the cooling demand varies with temperature.
Innovation Solution
A control unit adjusts the flow rate of a cooling fluid to the stator winding based on temperature, creating a cooling fluid level that optimally covers the stator winding, reducing drag losses and conserving pump energy by varying the fluid level and flow rate according to the stator winding's temperature and operational conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If coolant is continuously supplied to the electrical machine housing to cool the stator winding, then cooling effectiveness is improved, but drag losses increase due to rotor contact with coolant
Solution Approach 1:
The patent applies dynamics by making the coolant supply flow rate variable rather than constant. The control unit adjusts the coolant flow rate dynamically based on the electrical machine's operating state and temperature measurements, allowing the system to optimize between cooling effectiveness and drag losses depending on actual thermal conditions
Solution Approach 2:
The patent changes the parameter of coolant flow rate from a fixed value to a variable parameter controlled by a control unit. By adjusting this parameter according to temperature feedback and operating conditions, the system achieves optimal cooling while minimizing energy losses from rotor drag on the coolant
2Temperature
If high flow rate of cooling fluid is supplied to the stator winding, then cooling effectiveness is improved, but pump energy consumption increases
Solution Approach 1:
The patent implements feedback control where temperature sensors monitor the stator winding temperature and feed this information to a control unit. The control unit then adjusts the coolant flow rate accordingly, creating a closed-loop system that optimizes pump energy consumption by supplying only the necessary cooling flow rate required by actual thermal conditions
Solution Approach 2:
The system transitions from static high flow rate cooling to dynamic flow rate adjustment. The pump operates at variable speeds or flow rates based on real-time temperature conditions, consuming high energy only when high cooling demand exists and low energy when cooling demand is reduced
3Temperature
If coolant level in housing is increased to improve cooling coverage, then cooling of stator winding is improved, but drag losses on rotor increase
Solution Approach 1:
The patent changes the coolant level parameter from a fixed high level to a variable level. By controlling the coolant supply flow rate dynamically, the system adjusts the coolant level in the housing to match actual cooling needs, preventing unnecessary rotor drag while maintaining adequate cooling coverage of the stator winding
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures effective cooling of the stator winding with reduced drag losses and optimized energy usage, maintaining a uniform temperature and improving the overall performance of the electrical machine.
Implementation Method 1
A number of cooling devices generates a coolant spray on the stator during operation of the electrical machine
Implementation Method 2
the cooling fluid flows downward along the surface of the coil end and drops into an oil pan
Implementation Method 3
creating a cooling fluid level in the housing at which the cooling fluid covers at least a part of a lowest located portion of the stator winding
Data Source
Figure 1
Figure 2
AI summary
The present invention relates to an arrangement for cooling of an electrical machine (3). The electrical machine (3) comprises a rotor (5) rotatably arranged around a rotation axis (4a), a stator (6) including a stator winding (6b) arranged radially outside of the rotor (5), a housing (2) enclosing the rotor (5) and the stator (6), at least one drain hole (11) configured to drain a cooling fluid from the housing (2), at least one spraying device (8-10) configured to spray cooling fluid on the stator winding (6b) and a pump (14) configured to pump cooling fluid to the spraying device (8-10). The arrangement comprises a control unit (18) which is configured, when the electrical machine (3) is in operation, to receive information of the temperature in at least one position of the stator winding (6b) and to control the pump (14) such that it pumps a flow rate of the cooling fluid to the spraying device (8-10) which is related to the estimated temperature of the stator winding (6b).